Rotational casting apparatus



March '1966 w. s. EGGERT, JR., ETAL 3,237,247

ROTATIONAL CASTING APPARATUS Filed Nov. 8, 1963 2 Sheets-Sheet 1 Fig.2

62 CENTRIFUGAL FAN INVENTORS WALTER S. EGGERT, JR. HARRY M.RUSSEL-FRENCH I6 60 M Qh UQLJK March 1, 1966 w. s. EGGERT, JR., ETAL3,237,247

ROTATIONAL CASTING APPARATUS Filed Nov. 8, 1965 2 Sheets-Sheet 2INVENTORS WALTER S.EGGERT,JR. BY HARRY M. RUSSE L- FRENCH ATTORNEYUnited States Patent 3,237,247 ROTATIONAL CASTING APPARATUS Walter S.Eggert, Jr., and Harry M. Russell-French, Philadelphia, Pa., assignorsto The Budd Company, Philadelphia, Pa., a corporation of PennsylvaniaFiled Nov. 8, 1963, Ser. No. 322,287 Claims. (Cl. 18-26) This inventionrelates to apparatus for rotationally casting hollow objects of moldablematerials such as synthetic resins.

A conventional way of making hollow plastic objects is by rotationalmolding or casting techniques wherein a charge of a moldable material isplaced in a hollow mold that is simultaneously rotated about a pluralityof axes and heated to set the material in a relatively uniform coatingdeposited inside the mold. The present invention is directed torotational casting apparatus that is designed to carry out such aprocess, the apparatus comprising a rotary casting machine for rotatingthe mold and an oven for heating the mold, and one of the objects of theinvention is to provide a novel rotary casting machine and oven that iseasy to use, versatile, and can be operated to mold materials ofdiiferent molding characteristics.

Another object of the invention is to provide rotational castingapparatus wherein a mold is loaded and unloaded outside of an oven yetit can be readily placed in the oven and rotated to carry out steps ofthe molding process.

Still another object of the invention is to provide a novel rotarycasting machine for rotating a mold within an oven wherein the castingmachine comprises electric motors that are disposed outside of the ovenfor operation at room temperature.

A further object is to provide a novel forced circulation oven whichprovides rapid temperature changes within the oven.

Other objects and advantages of the invention will be apparent from thefollowing description taken in connection with the accompanying drawingswherein:

FIG. 1 is a perspective view of rotational casting apparatus embodyingthe invention;

FIG. 2 is a vertical elevational view, generally along lines 22 of FIG.3, partly in section, looking towards the inside of the front of theoven and;

FIG. 3 is an enlarged vertical, longitudinal, sectional view, withportions removed, taken generally on lines 33 of FIG. 2.

Referring now to the drawings, the illustrated rotational castingapparatus comprises a hollow, sectional mold 10, a rotary castingmachine 11, and an oven 12. The shape of mold 10 and the manner in whichit is mounted and rotated is dependent, obviously, 0n the shape of thearticle being formed. For simplicity of illustration, mold 10 is shownas a cylindrical mold formed in two detachable section-s having alongitudinal parting line. Such a mold is designed to form a hollowcylinder.

The purpose of rotary casting machine 11 is to support and rotate mold10 about a plurality of mutually perpendicular axes that intersectwithin the mold. To accomplish this, machine 11 comprises a rotary head13 mounted on a base or carriage 14 having a plurality of Wheels 15 thatroll on guiding rails 16 which extend perpendicularly to and in front ofoven 12. Carriage 14 further comprises a base plate 17 on which ismounted, in addition to wheels 15, a vertical pin 18 having its lowerend welded into a hole in the center of plate 17. The lower end of pin18 extends through an annular, upwardly facing thrust bearing 19 thatengages and supports the lower end of a rotatable, vertical sleeve 20fitted over pin 18 for rotation about the axis thereof. The upper end ofsleeve 20 carries a pair of cylindrical arms 21 and 22 whose axes arecoplanar with the axis of sleeve 20 and pin 18. Using the front of theoven as a reference, that is, the face of the oven facing to the left asviewed in FIG. 1, it will be seen that arm 21 extends rearwardly ofsleeve 20 and arm 22 extends forwardly, the free ends of these armscarrying a yoke 23 and an adjustable socket or gripper 24, respectively.

Rotary head 13 comprises a tubular cylindrical housing 26 that ispivotally attached by trunnions 27 at the rear end of the housing toyoke 23 for pivotal movement about a horizontal axis extending throughtrunnions 27. The other end of housing 26 has a pair of dependent lugs28 pivotally connected to the upper end of a downwardly extending rod 29that passes through and is detachably secured to gripper 24. Byloosening and tightening gripper 24, arm 29 can be moved vertically torotate or pivot housing 26 and rotary head 13 to the desired angularposition. In the illustrated embodiment, the range of angular adjustmentis approximately thirty-five degrees from a horizontal position and aninclined position. Obviously, this range can be varied to suit theparticular application desired.

Rotary head 13 further comprises a main tubular cylindrical drive shaft30 rotatably supported, by suitable bearings, in housing 26 in coaxialrelationship thereto. The length of shaft 30 is greater than the lengthof housing 26 and the ends of shaft 30 extend beyond the ends of housing26. The front end of shaft 30 carries a sprocket driven by a chain 32,that in turn, is driven by a sprocket connected to the output shaft of avariable speed, integral gear box and electric motor 33 mounted on asupport plate 34 Welded to the upper front end of housing 26, the gearbox having an overriding clutch permitting manual rotation in thedirection opposite to the driven direction.

The rear end of shaft 30 is connected to a transversely extending arm 35of rectangular tubing, having a counterweight 36 attached to one of itsends and a tubular, rearwardly extending arm 37 attached to its otherend. Arm 37 supports, at its rear end, a yoke 38 that rotatably supportsa rotary shaft 39 having a mold mounting plate 40 attached to itsradially inner end. Mold 10 comprises a U-shaped mounting member 41 thatis mounted on plate 40 by suitable releasable fasteners, e.g., bolts,and supports mold 10 so that the axes of rotation of shafts 30 and 39pass through the center of the mold and intersect each other at rightangles.

Shaft 39 is rotated about its own axis by a bevel gear 43 mountedthereon, the bevel gear being engaged with another bevel gear 44 mountedon a shaft 45 that is rotatably mounted coaxially to and within arm 37.At its front end shaft 45 carries a sprocket driven by a chain 46 which,in turn, is driven by a sprocket carried on the rear end of a driveshaft 47 rotatably mounted within and coaxial to shaft 30. Drive shaft47 is longer than shaft 30 and its ends project beyond the ends of shaft30. The front end of shaft 47 carries a sprocket driven by a chain 49connected to a sprocket carried by the output shaft of a variable speedgear box and electric motor 49 mounted on plate 34 alongside motor 33,the gear box having a manual override. C-hains 32 and 49 and thesprockets can be covered by a protective cover 50. Motors 33 and 49 canbe separately or simultaneously operated to rotate mold 10 about theaxis of shaft 30 and about the axis of shaft 39, respectively.

Carriage 14 further supports a flat, vertical enclosure member or ovenpanel 52 by means of a support plate 53 and an angle plate 54 mounted onsleeve 20 and bolted to a pair of vertically-spaced, angle members 55attached to the panel. Panel 52 has a first opening 56 through which arm21 passes, the opening being shaped to seal as much as possible thespace around the arm where it passes through the panel. The panel alsohas a second opening 57 vertically spaced above opening 56 through whichhousing 26 passes, this opening being shaped to permit angularadjustment of head 13. Opening 57 is partially sealed by an adjustableseal comprising two, vertically sli-d'able plates 58 and 59 mounted intracks on opposite sides of the panel and adjustable vertically so thattheir adjacent edges, cut out to conform to the exterior of housing 26as much as possible, abut housing 26.

Oven 12 is an electrically-heated, forced-air oven and is suported by aplurality of legs 60 above the floor whereby rails 16 and carriage 14extend beneath, in the manner illustrated in the drawings, when thepanel is in place. As best seen in FIG. 2, oven 12 has a main heatingchamber 61 in which mold is rotated and heated and through which forcedair is circulated by means of a centrifugal fan 62. The circulated airis heated by an electric resistance heater 63 placed at the outlet offan 62 and the inlet into chamber 61, and an electric resistance heater64 mounted at the outlet of the chamber 61. Mounted above heater 64 area plurality of arcuate deflectors 65 that aid circulation of the airthrough the oven.

Oven 12 further comprises a fresh air inlet 66 and an exhaust outlet 67connected to a suitable exhaust stack 68. The flow of air through theinlet and outlet is controlled by a movable valve member or damper 69that is movable, upon actuation of a handle 71, between the positionsshown in full lines and dotted lines in FIG. 2 to recirculate airthrough or dump air from the heating chamber. The controls for thecentrifugal fan and heaters can be contained in suitable control boxes70 mounted on the outside of the oven.

Mounted on the front of the oven are two doors 72 and 73 hinged forrotation about vertical axes. The doors are laterally spaced to definean opening which panel 52 is adapted to cover when it is in the positionillustrated in the drawings. Doors 72 and 73 support a pair of hooks 74that cooperate with a latch bar 75 to allow doors 72 and 73 and panel 52to be locked to close the front of chamber 61,

Operation At the start of a molding cycle, carriage 14 is rolled awayfrom oven 12 to a position where the rotary head 13 can be pivoted to aloading station at one side of the tracks where mold is attached to thecasting machine. The mold can be either charged prior to attaching orafter it has been attached with a charge of a moldable plastic material.Thereafter, the sleeve 20/ is rotated back to the position where panel52 extends parallel to the front of the oven. Then, carriage 14, isrolled along rails 16 until panel 52 abuts the oven, doors 72 and 73 areshut, and latch bar 75 is placed in position to lock the doors andpanel. Next, motors 33 and 49 are actuated to rotate mold 10 in thedesired manner and the centrifugal fan 62 and heaters 63 and 64 areenergized to circulate heated air through chamber 61. During the heatingcycle, valve member 69 is located in the position shown by full lines inFIG. 2 so that air is merely recirculated through the oven. As thematerial is heated and as it passes over the inner surfaces of mold 10,it sets, in a manner dependent on the particular material. After thematerial initially sets, the rotation can be stopped and the mold keptin the oven until the material fully sets such as by polymerizing.Thereupon, heaters 63 and 64 can be deenergized and valve member 69 isrotated to the position shown in the dotted lines whereupon cool air issucked into the oven through inlet 66 and is blown through chamber61,.outlet 67 and stack 68. When the oven and mold have been cooledsufiiciently, the centrifugal fan is stopped, latch bar is removed, andthe carriage is withdrawn or moved away from the oven. Thereupon, themold along with the formed object, are removed.

Although it will be apparent that the apparatus can be used torotationally cast a wide variety of materials and synthetic resins, suchas the vinyl polymers, polyethylene, etc. the particular apparatusdisclosed was designed for rotationally casting caprolactum which uponpolymeriza tion produces nylon-6. With this particular material, theoven was designed to circulate air at a maximum rate of 5,000 cu. ft.per minute, at a pressure head of p.s.i. and at a maximum temperature of500 F. To achieve such temperatures, heaters were provided havingcapacities of 15.3 kw. and 25.5 kw.

While only a single embodiment has been illustrated, it will be apparentto those skilled in the art that many changes can be made in the detailsand arrangement of parts without departing from the scope of theinvention as defined in the appended claims.

What is claimed is:

1. In apparatus for rotationally casting a hollow plastic object in ahollow sectional mold, the combination comprising: an oven provided witha heating chamber and an opening communicating with the said chamber; abase disposed adjacent to said oven; an enclosure member mounted on saidbase and adapted to close said opening; and a rotary casting machinemounted on said base and extending through said enclosure member, saidmachine comprising rotatable support means located on one side of saidenclosure member and adapted to support and rotate the mold in saidchamber about a plurality of axes, and motor means mounted on the otherside of enclosure member and operatively connected for rotating saidsupport means.

2. The combination of claim 1 wherein said base comprises a wheledcarriage moveable toward and away from said oven, and said ovencomprises means for locking said enclosure member in place so as toprevent movement of said carriage and enclosure member away from saidopening.

3. Rotational casting apparatus, comprising: an oven provided with aheating chamber, an opening extending into said chamber, means forcirculating air through said chamber, and means for heating aircirculated through said chamber; guide rail means disposed adjacent tosaid oven and aligned with said opening; a carriage mounted on saidguide rails means for movement relative to said oven between a firstposition spaced from said oven and a second position adjacent to saidoven; an oven panel mounted on said carriage and adapted to close saidopening when said carriage is in said second position; and a rotarycasting machine mounted on said carriage and adapted to support a moldon one side of said panel for rotation about a plurality of axes, saidrotary machine extending through said panel and comprising motor meanslocated on the other side of said panel and operatively connected forrotating said mold.

4. Rotational casting apparatus comprising: an oven provided with a mainheating chamber and an opening communicating with said chamber; acarriage mounted for movement towards and away from said opening; an

oven panel mounted on said carriage and adapted to close said opening onmovement of said carriage theretowards; and a rotary machine mounted onsaid carriage and adapted to support and rotate a mold in said heatingchamber, said machine comprising mounting means for the mold disposed onone side of said panel, motor means disposed on other side of saidpanel, a housing extending through said panel, and means driven by saidmotor means for driving said mounting means and extending through saidhousing.

5. In an apparatus for rotationally casting, the combination comprising:a forced air, electric resistance oven having a main heating chamber andan opening communicating directly with said chamber; a rotary castingmachine adapted to support and rotate a mold about a plurality ofmutually perpendicular axes in said chamber, said rotary casting machinehaving a housing extending through said panel, motor means mounted onone end of said housing, a mold mount, and means connected to said motormeans and said mold mount for rotating said mold mount in response tooperation of said motor means; support means disposed outside of saidoven supporting said rotary casting machine and including means foradjusting the inclination of said housing; and an oven panel mounted onsaid support means and adapted to close said opening.

6. The combination of claim 5 wherein said panel comprises an adjustableseal for sealing the space where said housing passes through said panel.

7. The combination of claim 5 wherein said support means comprises awheeled carriage movable towards and away from said oven, and thecombination further includes releasable lock means engageable with saidpanel for preventing movement of said carriage away from said oven.

8. The combination of claim 7 and further including guide rail meansaligned with said opening and supporting said carriage for movementtherealong.

9. The combination of claim 8 wherein said support means comprises asupport member rotatable about a vertical axis and supporting said paneland said rotary casting machine.

10. The combination of claim 5 wherein said oven comprises a flowpassage having an inlet and outlet communicating with said main heatingchamber, an exhaust outlet and a fresh air inlet; said oven furthercomprising a valve member movable between first and second positionswherein air is recirculated through said heating chamber and is dumpedfrom said chamber, respectively.

References Cited by the Examiner UNITED STATES PATENTS 2,629,130 2/1953Remble l826 2,681,472 1/ 1954 Remble l826 2,958,907 11/1960 Mumford eta1 l826 3,072,965 1/1963 Miller l826 WILLIAM J. STEPHENSON, PrimaryExaminer.

1. IN APPARATUS FOR ROTATIONALLY CASTING A HOLLOW PLASTIC OBJECT IN AHOLLOW SECTIONAL MOLD, THE COMBINATION COMPRISING: AN OVEN PROVIDED WITHA HEATING CHAMBER AND AN OPENING COMMUNICATING WITH THE SAID CHAMBER; ABASE DISPOSED ADJACENT TO SAID OVER; AN ENCLOSURE MEMBER MOUNTED ON SAIDBASE AND ADAPTED TO CLOSE SAID OPENING; AND A ROTARY CASTING MACHINEMOUNTED ON SAID BASE AND EXTENDING THROUGH SAID ENCLOSURE MEMBER, SAIDMACHINE COMPRISING ROTATABLE SUPPORT MEANS LOCATED ON ONE SIDE OF SAIDENCLOSURE MEMBER AND ADAPTED TO SUPPORT AND ROTATE THE MOLD IN SAIDCHAMBER ABOUT A PLURALITY OF AXES, AND MOTOR MEANS MOUNTED ON THE OTHERSIDE OF ENCLOSURE MEMBER AND OPERATIVELY CONNECTED TOF ROTATING SAIDSUPPORT MEANS.